Astronomija kratka povijest problematike

Transcription

1 Astronomija kratka povijest problematike

2 Područje interesa Planeti Sunčev sustav Zvijezde Međuzvjezdani prostor Galaksije aksije Aktivne galaktičke ke jezgre (AGN( AGN) Kvazari (eng. quasar - quasi-stellar stellar radio source) Klasteri galaksija Pulsari (brzorotirajuće neutronske zvijezde) Svemir

3 Sunčev sustav Fizika Sunca Solarni vjetar Planeti Njihovi sateliti Asteroidi NEOs (eng. Near eart objects) Pojasi Interplanetarna arna prašina

4 Zvijezde promjenjive zvijezde dvojne zvijezde patuljci, divovi Supernove kompaktni objekti (crne rupe, bijeli patuljci, neutronske nske zvijezde)

5 Međuzvjezdani prostor Nastanak zvijezda Astro-kemija Struktura i razvoj zvijezda Nuklearna astrofizika

6 Galaksije Nastanak i formiranje Struktura Naseljenost Dinamika

7 AGN (Aktivne galaktičke ke jezgre) Kvazari nastanak klasifikacija gorivo evolucija gustoća

8 Klasteri Nastanak i razvoj Struktura Tamna tvar Gravitacijske leće

9 Svemir Starost i veličina ina Nastanak i razvoj Tamna materija, stringovi,, egzotične čestice Topologija (oblik)

10 Znanstveni elementi u astronomiji Promatranje Zemaljsko (opti optičko, infracrveno crveno,, radio) Vanplanetarno (sateliti i satelitske platforme; ; UV, x-ray) x Računanje Analiza podataka Kompleksni problemi Numeričke simulacije Analiza objektivnost asimiliranje iranje formi i podataka linearno no & nelinear linearnono razmišljanje Pisanje publikacija prijedloga prezentacija

11 Zapošljavanje (danas)

12 Što astronomi ne rade Pišu u horoskope Imaju vezu s vanzemaljskim civilizacijama Memoriraju konstelacije Cijelo vrijeme gledaju kroz teleskop

13 Radioastronomija Kozmičko zračenje 3K

14 Elektromagnetski valovi

15 E=h c= Duži valovi Niža energija Niža frekvencija Kraćo valovi Veća energija Viša frekvencija

16 Elektromagnetski spektar

17 Elektromagnetski prozor kroz atmosferu!

18 Izvori elektromagnetskog zračenja Termalni Zračenje crnog tijela Kontinuirana emisija ioniziranog plina (plazma) Emisija spektralnog zračenja atoma i molekula Netermalni Sinkrotronsko zračenje MASERS

19 Plankov zakon u(ν,t) = 4 I(ν,T) / c

20 Zračenje crnog tijela - Sjaj

21 Sjaj elektromagnetskog zračenja različitih itih valnih dužina za crno tijelo na različitim itim temperaturama

22 MASER

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24 Sinkrotronsko zračenje Polarizacojska svojstva EM zračenja daju informacije o geometriji magnetskog polja

25 Sinkrotronsko zračenje

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27 Zakon obrnutog kvadrata!

28 Zabluda Radio program koji se ne sluša!

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30 Radio Teleskopi Dvije izvedbe: Green Bank Telescope, WV Very Large Array, NM Radio antena Polje radio antena

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32 The Very Large Array (VLA) 1980 godine Dvadest sedam 25-metarskih rekonfigurabilnih antena; a; Socorro, NM Više e publikacija od bilo kojeg teleskopa na svijetu

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34 Very Long Baseline Array (VLBA) 1993 godine Operirane oz Socorro-a Deset 25-m antennas diljem SAD, Kanade,, P.R. Najviša rezolucija

35 Počeci eksperiment Janskog Promatra nemodulirani doprinos RF (static) Postepeno s mijenja intenzitet s periodom od gotovo 24h Sunce izvor? maksimum 4 minute rani svaki dan Izvor izvan Sunčeva sustava Izvor u Mlječnoj stazi! 1933 objavljuje rezultate Karl G. Jansky ( )

36 Reberov tip radioteleskopa Despite the implications of Jansky s work, both on the design of radio receivers, as well as for radio astronomy, no one paid much attention at first. Then, in 1937, Grote Reber, another radio engineer, picked up on Jansky s discoveries and built the prototype for the modern radio telescope in his back yard in Wheaton, Illinois. He started out looking for radiation at shorter wavelengths, thinking these wavelengths would be stronger and easier to detect. He didn t have much luck, however, and ended up modifying his antenna to detect radiation at a wavelength of 1.87 meters (about the height of a human), where he found strong emissions along the plane of the Milky Way.

37 Reconfigurable Arrays: Zoom Lens Effect VLA VLBA Više detektora bolja rezolucija

38 Radio Telescopes: Sensitivity Sensitivity (how faint of a thing you can see ) depends on how much of the area of the telescope/array is actually collecting data VLA B-array: B Total telescope collecting area is only 0.02% of land area More spread-out arrays can only image very bright, compact sources

39 Parabolic Dish Green Bank Telescope, WV Aluminum reflecting surface Focuses incoming waves to prime focus or sub-reflector Sub-reflector

40 Sub-reflector Subreflector Re-directs incoming waves to Feed Pedestal Can be rotated to redirect radiation to a number of different receivers Feed Pedestal

41 1.5GHz 20cm 2.3GHz 13cm 4.8GHz 6cm 8.4GHz 4cm 14GHz 2cm 23GHz 1.3cm 43GHz 7mm 86GHz 3mm Feed Pedestal 327MHz 90cm 610MHz 50cm

42 Antenna Feed and Receivers

43 Benefits of Observing in the Radio Track physical processes with no signature at other wavelengths Radio waves can travel through dusty regions Can provide information on magnetic field strength and orientation Can provide information on line-of of-sight velocities Daytime observing (for cm-scale wavelengths anyway)

44 Primary Astrophysical Processes Emitting Radio Radiation When charged particles change direction, they emit radiation Synchrotron Radiation Charged particles moving along magnetic field lines Thermal emission Cool bodies Charged particles in a plasma moving around Spectral Line emission Discrete transitions in atoms and molecules

45 Thermal Emission Emission from warm bodies Blackbody radiation Bodies with temperatures of ~ K emit in the mm & submm bands Emission from accelerating charged particles Bremsstrahlung or free-free emission

46 Nobelova nagrada za otkriće kozmičkog kog mikrovalnog pozadinskog zračenja Arno Allan Penzias Robert Woodrow Wilson

47 The Nobel Prize in Physics 1993 for the discovery of a new type of pulsar,, a discovery that has opened up new possibilities for the study of gravitation" Russell A. Hulse Joseph H. Taylor Jr

48 Transition probability=3x10-15 s -1 = once in 11 Myr Spectral Line emission: hyperfine transition of neutral Hydrogen Emits photon with a wavelength of 21 cm (frequency of 1.42 GHz)

49 Spectral Line emission: malondialdyde molecular rotational and vibrational modes Commonly observed molecules in space: Carbon Monoxide (CO) Water (H 2 O), OH, HCN, HCO +, CS Ammonia (NH 3 ), Formaldehyde (H 2 CO) Less common molecules: Sugar, Alcohol, Antifreeze (Ethylene Glycol),

50 Spectral Line Doppler effect Spectral lines have fixed and very well determined frequencies The frequency of a source will changed when it moves towards or away from you Comparing observed frequency to known frequency tells you the velocity of the source towards or away from you Sees longer wavelength Sees shorter wavelength Sees original wavelength

51 NASA s Goldstone Solar System Radar Very Large Array Special example of Spectral Line observation: Doppler Radar Imaging bounce off object Transmit radio wave with well defined frequency..observe same frequency

52 Brief Tour of the Radio Universe Solar System Sun, Planets, Asteroids Galactic objects Dark clouds, proto-stellar disks, supernova remnants, Galaxies Magnetic fields, neutral hydrogen Radio Jets The Universe

53 Wilkinson Microwave Anisotropy Probe (WMAP) map.gsfc.nasa.gov K-band Ka-band Q-band V-band 23 W-band GHz GHz GHz GHz Background=3 K blackbody radiation Shepherding in the era of Precision Cosmology

54 Radio pregled Mlječne staze

55 (a) radio (b) infrared, (c) visible (d) X-ray Each illustration shows the Milky Way stretching horizontally across the picture.

56 Pulsar Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation.. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name. Because neutron stars are very dense objects,, the rotation period and thus the interval between observed pulses are very regular. For some pulsars,, the regularity of pulsation is as precise as an atomic clock. Pulsars are known to have planets orbiting them,, as in the case of PSR B Werner Becker of the Max-Planck-Institut für extraterrestrische Physik said in 2006, "The theory of how pulsars emit their radiation is still in its infancy, even after nearly forty years of work."

57 Kvazar A Quasi-stellar stellar radio source (Quasar)) is a powerfully energetic and distant galaxy with an active galactic nucleus. Quasars were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were pointlike, similar to stars, rather than extended sources similar to galaxies. While there was initially some controversy over the nature of these objects as recently as the 1980s, there was no clear consensus as to their nature there is now a scientific consensus that a quasar is a compact region 10-10,000 Schwarzschild radii across surrounding the central supermassive black hole of a galaxy, powered by its accretion disc.

58 Maser Historical background In 1965 an unexpected discovery was made by Weaver et al. - emission lines in space of unknown origin at a frequency of 1665 MHz.. At this time many people still thought that molecules could not exist in space,, so the emission was at first put down to an interstellar species named Mysterium, but the emission was soon identified as line emission from OH molecules in compact sources within molecular clouds.. More discoveries followed, with H2O emission in 1969, CH3OH emission in 1970 and SiO emission in 1974[7] [7],, all coming from within molecular clouds. These were termed "masers", as from their narrow line-widths and high effective temperatures it became clear that these sources were amplifying microwave radiation. Masers were then discovered around highly evolved Late type stars; First was OH emission in 1968, then H2O emission in 1969 and SiO emission in Masers were also discovered in external galaxies in 1973, and in our own solar system in comet halos. Another unexpected discovery was made in 1982 with the discovery of emission from an extra-galactic source with an unrivalled luminosity about 106 times larger than any previous source. This was termed a megamaser because of its great luminosity, and many more megamasers have since been discovered. Evidence for an anti-pumped (dasar) sub-thermal population in the 4830 MHz transition of formaldehyde (H2CO) was observed in 1969 by Palmer et al.

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62 has the most precise thermal emission spectrum known and corresponds to a temperature of kelvin (K) with an emission peak at GHz